1. Field of the Invention
This invention relates to a heart-lung machine for pumping blood out of a patient's body for blood treatment and returning the treated blood to the patient's body.
2. Description of Prior Art
Extracorporeal circulation type heart-lung machines have been known, for example, from Japanese Patent Publication H2-12108 disclosing a heart-lung machine which is composed of a series of separably connected operating units including an artificial lung unit for refreshing blood through oxidation, and a heat exchanger unit in which heated water is circulated to maintain the blood at a predetermined temperature, and also from Japanese Laid-open Patent Application H2-41172 disclosing a heart-lung machine which has a blood treating section (i.e. an artificial lung) and a blood feed mechanism integrally incorporated into outer and inner portions of a cylindrical casing, respectively, such that blood, inflowing through an apex portion of a blood guide member of a substantially conical shape, is discharged through a blood discharge port by rotation of a rotary member for introduction into the blood treating section and then being allowed to flow out through a blood outlet on the downstream side, the blood treating section being interiorly provided with a heat exchanger for circulation of a heat exchanging medium therethrough.
In the former case where the blood pump, artificial lung and heat exchanger are connected in series as separable operating units, however, the machine involves a lengthy flow passage for the blood to be treated and necessitates providing a support stand exclusively for fixedly retaining the position of the machine body. In this connection, since it is difficult to install the machine in a sanitary region in the vicinity of a patient and since the heat exchanger unit needs a separate heat source, difficulties are often encountered in reducing the volume of the blood in the feed system or the blood pumped to a marked degree, coupled with the inconvenient and troublesome job of connecting inflow and outflow tubes for the heat exchanging medium to and from the heat exchanger unit.
Further, in the latter case, blood strikes against guide blades under the influence of the centrifugal force of the pump, and, as the blood is introduced into the artificial lung at a high velocity under the guidance of the guide blades, it vigorously strikes the casing of the artificial lung at the blood inlet thereof and also against hollow yarns of the lung. It follows that the blood is susceptible to destruction of blood cells (hemolysis) due to physical stresses.